The performance of computational components and storage devices in computing systems, such as personal computers and rack mounted servers, require effective cooling mechanisms to ensure that the components and devices used inside operate in a preferred temperature range. The operational stability of central processing units (CPUs), video processing units, memory and storage devices, for example, can be adversely affected by heat accumulation within enclosed spaces in which they are housed, such as encountered in relatively thin notebook computers. With each newly introduced computing system, the performance of components used internally are being increased, while simultaneously, the dimensions of the external enclosure that houses the computing system are being decreased, thereby challenging the computer system designers to devise more efficient cooling methods. The narrow height dimensions of portable computer housings can require more efficient cooling methods than can be provided by thermal conduction alone or even when combined with conventional air circulation fan designs.
Air circulation fans within computing systems can include axial fans that move air parallel to the rotational axis of the fan's impeller and centrifugal fans that blow air through an outlet perpendicular to an air inlet opening. Several geometric properties of a centrifugal fan's shape can affect its air flow performance, including the size, shape and orientation of the air inlet opening through which air is drawn when rotating the fan's impeller. In a typical prior art centrifugal fan, a circular inlet opening in the fan's housing is positioned concentric with the rotational axis of an impeller situated inside the fan housing. Increasing the diameter of the circular inlet opening beyond a certain size can decrease air flow (rather than increase it as intended) due to air being expelled upward from the rotating impeller blades and thereby forcing some air out of the inlet opening rather than drawing air in. Prior art methods have designed variously shaped inlet openings for centrifugal fans to change the fan's air flow. Such ad hoc methods can change the air flow but not necessarily maximize the flow rate through the fan in its intended application. None of the prior art methods known to the applicants have systematically designed the inlet opening according to calculated pressure contour profiles on the fan housing's surface operating in situ. Thus there exists a need for an improved method to form an inlet opening in a cooling fan to maximize flow rate.